Visibility threshold device for indicating changes in the oxygen content of air



May 9, 1950. J. c. HARTLEY 2,506,591

Y VISIBILITY THRESHHOLD DEVICE FR INDICATING CHANGES 1N TEE OXYGENCONTENT 0E AIR Filed Deo. 30, 1947 /NvE/vmle.-

,JOHN C A nemer E f lf. 5 a Hrw-oe Patented May 9, 1.950

-'llie invention 'described herein-may be manufactured and used by orfor the Government of the United States for governmental purposeswithout the payment to me of any royalty thereon in accordance with theprovisions of the Act of March 3, 1883, as amended April 30, 1928.

My device provides a method and apparatus for promptly indicating adeficiency of oxygen in a restricted space such as a coal or metal mine,or a sewer, a manhole, or an empty petroleum products storage tankliable or suspected to contain air decient in oxygen, by means of thereduction in the intensity of illumination produced by a flame when theoxygen content of the air is lowered. Wherever warned by my device ofany dangerous compositi-on of the air, an inspector should seek thecause and correction of the dangerous condition without the delay andexpense incident to collecting` a sample for a laboratory quantitativeanalysis.

Fluctuations in the intensity of illumination given oi by a miners lampwhen transported from place to place are dicult to measure by theunaided eye. I provide an opaque shield for attachment to suspendingrods of a miners lantern, or the like, with a plurality of light liltersof different degrees of light-stopping power, mounted over transverseapertures in said shield,

The shield is mounted at a iixed distance from the center of the iiameof the lantern then a plurality of light filters are selected Which willstop all light from the flame whenever the percentage of oxygen falls toone of a plurality of predetermined minimums. When no light is passed byany of the light filters, a dangerous condition is indicated whichdemands prompt correction.

When methane or other inammable gas is present in the air within a mine,the ame f a miners safety lamp lengthens which intensies the heatapplied to bi-metallic warning devices with which the improved minerssafety lamps are equipped so that with my attachment for Warning thatthere is a deiiciency of oxygen, an inspector can quickly detect boththe presence of inflammable gas o-r a deficiency of oxygen.

In the accompanying drawings which illustrate a preferred form of mydevice:

Figure 1 is an elevation of the device.

Figure 2 is an elevation of a miners safety lamp with my device attachedthereto.

Figure 3 is a section on the line 3-3 of Figure 1.

Fig. 4 is an elevation of a modified form of the device.

In these drawings:

An opaque shield formed of two curved layers 'amended April: 30,' 1928#BEHISLO.` 6:41757??A I I I Ztis provided'v transverse'apertures- I3? I4,I5, and I6. Each aperture is closed by one of a plurality of lightstopping lters I1, I8, I9, and 2l); each of said filters having av'diierent light stopping power from that of the companion filters. Theshield layers II I2 are formed with rod clamping extensions 2|; 22 onone side and a reinforcing rib 23 on Vthe opposite side, all being heldtogether by suitable rivets 24, or the like. It will be observed thatthe margin to which the rib 23 is attached is made concave.

My device is attached to a. standard miners safety lamp 25 by forcingthe clamping extensions 2|; 22 against one of the lamp suspending rods26 and due to the resilience of the material, these extensions willyield to admit the rod, then by springing the flexible shield II toforce the opposite side against an adjacent rod 26 secure the devicetransversely of a zone of illumination from the burner 21 of the lamp.When so mounted on the lamp, my device remains at a constant fixeddistance from the flame of the burner 21 and in its application to lampsof different types and construction, the density of the filters isdependent on the intensity of illumination on the inner surface of myshield, said intensity varying as the square of the distance between theshield and the iame of the burner while the oxygen content of the airremains constant.

A mirror 28 may be mounted on the lamp 25 at an angle of 45 degrees tothe vertical axis of the lamp by means of suitable brackets 29. Theshield serves to cut off a direct view of the ame so that by looking atthe lters it may be readily determined Whether or not light is passingthrough one or more of the lters. Before entering a manhole or a storagetank which may contain air which is deficient in oxygen, a Workman maylower a miners lamp equipped with my shield and cooperating mirror 28into the tank or the like while Watching the mirror for an dangerindication.

It should be understood that the present disclosure is for the purposeof illustration only, and that the invention includes all modicatlonsand equivalents which fall within the scope of the appended claims.

What I claim is:

1. In a device for indicating changes in the composition of air in arestricted space by means of fluctuations in the intensity ofillumination produced by the ilame of a miners lamp or the like, theimprovement which comprises an at-A tachment for a miners lamp includingan opaque shield formed of two layers each having a plurality o!apertures, means for fastening said layers together with the aperturesin one layer in alignment with those of the companion layer. said shieldbeing formed with a curvature substantially concentric with the centerof the ame of the laip lateral extensions 0n each layer adapted toengage suspending rods of a miners lamp, when the layers are clampedtogether, and a plurality of aperture closing light filters mountedbetween said layers, each of a diierent lightstopping power from theremaining filters.

2. In a device for indicating a deciency of the oxygen content of air ina restricted space by means of fluctuations in the intensity ofillumination produced by a flame of a portable lamp of the safety lamptype provided with substantially vertical spaced rods, the improvementwhich comprises a shield of two layers of opaque material provided witha plurality of aligned apertures, a light lter closing each aperture anddiiering in light-stopping power from each of 4 the other filters, saidfilters being retained between said layers of said shield, said shieldlayers being formed with a curvature substantially concentric with thecenter of the ame of the lamp when in operative position with lateralmargins curved to fit suspending rods of said lamp, and means foruniting said shield layers. JOHN CURTIS HARTLEY.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date 1,460,055 Drew June 26, 19231,728,838 Stair Sept. 17, 1929 2,063,222 Beam Dec. 8, 1936 2,147,902Jakosky Feb. 21, 1939 2,244,507 Thomas June 3, 1941 2,440,266 Hall Apr.27, 1948

